The invention relates to television standards conversion.
Standards conversion generally involves rearrangement of the television picture so that the incoming television standard has a different field and line frequency to the outgoing television standard. For example, a PAL to NTSC standards converter has an incoming line standard of 625 lines per frame whereas the outgoing standard has 525 lines per frame. One requirement is that the picture information contained in each frame is processed to give the correct number of lines for the outgoing frame.
A second requirement for a standards converter concerns the difference between the incoming and outgoing frame or field rates. A European PAL standard uses 50 fields per second whereas an NTSC standard used in the USA has 60 fields per second. Both standards of field rate are sufficiently fast to prevent flicker between successive fields being detected by the viewer. However, each field may be considered as a completely new picture which steadily builds up the movement which may be contained in the scene.
When undertaking standards conversion from one field rate to another field rate difficulties may be encountered due to distortion of movement information unless steps are taken to minimise the problem.